As for a device attached to an upper end of a filler pipe (also called an inlet pipe and the like), and opening by an insertion of a fuel filling nozzle of a fuel filling gun so as to feed fuel, there are devices shown in Patent Documents 1 and 2.
The device of the Patent Document 1 includes an upper valve member pushed to open by the fuel filling nozzle, and a lower valve member. Thereby, a screw-type fuel inlet cap is unnecessary. However, the valve member of the Patent Document 1 has a structure of turning around one axis, so that a space for allowing the turning to an open position of the valve member which is necessary below the valve member cannot be minimized.
On the other hand, in the device of the Patent Document 2, a dust flap which becomes an upper valve member is formed by a pair of semicircular flaps, and each of the flaps has a structure turnably supported in a portion opposite to a portion abutting against the other of the flaps in a closed position so as to minimize a space for allowing the flap to turn to an open position which is necessary below the flap.
However, in the aforementioned devices, the aforementioned space is inevitably necessary below the upper valve member opening by the insertion of the fuel filling gun. Consequently, if the devices are simply formed, although the inserted fuel filling nozzle opens the upper valve member, the inserted fuel filling nozzle may not be able to open the lower valve member by abutting against an opening edge portion of a pass-through opening closed by the lower valve member and the like.